The clarion. [volume] (Jackson, Miss.) 1883-1888, 1887-07-06
Forests and Rainfall.

The tangle of decaved vegetation
which covers the ground beneath the
forest Is of considerable thickness.
On the top il consists altogether of
the decayed trunks, branches and
leaves, but it shades downward into
ordinary dark-colored soil. at depth
of few feet from the surface. This,
the decay zone of the forest, lies be-
tween the boughs Of the air and the
branches Of the roots. In it 20 on the
most important actions which take
place in our forests-actions which af-
feet the history of land and sea. We
shall therefore have to consider it in a
somewhat painstaking way. The most
evident effect of this sheet of decay
ing wood and moss which feeds on the
decay, is on the rainfall Of the region
which it manties. When, after sea
son of drought, a copious rain falls on
this spongy mass, the water is for a
long time absorbed in the interstices,
and docs not flow 10 the rivers Even
in times of heavy rain the water is
slowly yielded to the streams; after a
dry period of many weeks this sponge
retains a good share of water A like
amount of water falling on titled
fields or prairies slips quickly away tc
the rivers and thence to the sea The
first result is that when the land is
destitute of forests it sheds water like
house roofs, breeding floods after every
considerable rain, while in the forests
the rain is only slowly yielded to the
streams.
A second and less evident result ot
the spongy character of the forest BED
is that, by hindering the escape of the
| rain-water to the rivers, it increases
the actual rainfall of the country. TC
see the nature and Importance of thi,
action we must turn aside for a mo-
ment to consider the origin of the
rain which falls upon the land TIL,
| original source of this water supply i,
| the sea, which sends into the lands
| tolerably regular supply annually o
moisture. When this falls as rain ol
snow, either of the two things may
| happen-the water may go away di
| rectly to the sea, or it may return Il
the atmosphere as vapor, to be agair
precipitated as rain. The chance O
| the re-evaporation is determined by
the speed with which it flows to the
streams. From a treeless region i
rapidly escapes; in an extensive regiOI
of virgin forest it may again an(
again pass from earth to air, and from
| air to earth.
The columns of vapor, which il
| times of summer rain may be seer
ascending from every great wood, af
ford visible evidence of the effect @
the forests on rainfall. They also ma,
| show the observer some of the mos
beautiful phenomena of atmosphere
| circulation. In summer rain Shove
| the air above the trees becomes mucl
| cooler than it is in the reccsses below
| their tents of foliage. The heated al
within the woods seeks to rise and es
| cape in great columns whenever ther
is "A wide gap between the branches
as soon as it attains the cooler leve
| above, the moisture is condensed, ant
the air, before transparent, become
surcharged with steam. To replac
this ascending air a broad curren
drifts toward the emerging stream o
vapor, commonly from the highes
parts of the forest, where the air, ow
ing to the elevation of the site, is coole
than in the lower levels.
The repeated passage of the moist
to earth, greatly increases the amour
| of force which the rain applies in it
falling drops to the earths surface
but the rank vegetation protects tn
| surface from the erosion which
would otherwise bring about. Eve
| the forest clad hillsides of the Cum
| berland mountains where the soil lie
on declivities of great steepness, sui
| fer little wear as long as their natura
| protection is left to them. But a
soon as they are stripped of the gan
! ment of wood which has been upo
| the region ever since, in the far o.
| ages, they came from the depths c
the sea, they wear with great rapid
| ity. The erosion is limited, as the
| are forest clad, to the stream beds, an
there is hindercd by the innumerabl
| obstacles of the fallen trees and en-
tangled driftwood. The brooks which
| are strong enough to clear their beds
and cut into the earth and rock are
few in number; we may often, on the
| flatter ground, find tracts of square
mile or so in area in which there is moi
| a single stream that ever assails the
surface of the earth. As soon, how
| ever, as the forest mat is removed, the
| surface becomes scanned with chan
| nels; they often, on the deforested sur
| face, increase one hundred fold IL
their length and more than that meas
ure in their destructive power. Re
| lieved of all restraint from fallen tim
| Der, of the close knit roots which i'm
mesh the earth, they sweep preciou:
soil away toward the sea. In single
day a titled field may lose from it!
surface more soil than would be taker
from it in century of its forest state
| -ScribueT'S Ha0dziRe